There is a demand for more compact and more light weight cooling apparatus as electronic equipment becomes smaller. This tendency inevitably requires more compact cooling structures. In the case of an extrusion-molded structure having a comb-shaped cross section, however, the thickness and height of the cooling fins are limited due to restrictions in the relevant fabrication processes. Specifically, there have been some technological limits that prevent the space between the fins from being made narrower and prevent the heat-radiating surface area from being made larger. For this reason, to make the heat-radiating surface area larger, generally a compact cooling body with a high cooling efficiency is made by joining a plurality of plates or fins by brazing in a vacuum.
FIG. 24 is a perspective view illustrating the configuration of a conventional cooling apparatus, FIG. 25 is a perspective view of a fin constituting the fin section shown in FIG. 24, and FIG. 26 is a side view illustrating configuration of the fin section shown in FIG. 24. In the figures, the reference numeral 1 indicates a cooling body, the reference numeral 2 indicates a flat plate made of aluminum alloy, and the reference numeral 3 indicates a fin comprising brazing sheet plates each having a core material made of aluminum alloy and a brazing material provided on one face thereof. Herein the brazing sheet is made by rolling a brazing material on one face or both faces of an aluminum plate as a core plate.
The cooling body 1 is built by providing a plurality of fins 3 on and brazing them to the flat plate 2 in a vacuum. If any defect, including bending, occurs when brazing the fins 3 in a vacuum, the surface of the flat plate 2 constituting the cooling body 2 is flattened by, for instance, scraping a mounting surface 2a on which components are mounted to overcome the defects including said bending. The reference numerals 4a, 4b and 4c indicate a semiconductor for power, which is one of parts of the heat-radiating electronic equipment, respectively, and are placed on and tightened with a screw 5 to the mounting surface 2a. The reference numeral 6 indicates a cooling fan which sends air to the fins 3 of the cooling body 1 for air-cooling.
In order to achieve the maximum cooling efficiency in the fin 3, a proper relation of the fin plate thickness (t) and inter-fin space (p) with the fin height (h) (Refer to FIG. 25 and FIG. 26) is calculated, and the brazing sheet material is bent into a ]-shaped form with the brazing material in the outer side so that the dimension of the brazing sheet material is equalized to the inter-fin space (p) as well as to the fin height (h). The ]-shaped fins 3 are arrayed in parallel on the flat plate 2 and positioned so that a cross section 3b of a shorter edge section of a ]-shape in one fin 3 contacts a surface of a brazing material 3a in the outer side of a longer edge section of another fin 3. When all the fins 3 have been arrayed in parallel on the flat plate 2, the fins 3 are temporally fixed with an appropriate tool, temperature is raised in a vacuum furnace, and a shorter edge section 3c is brazed to the flat plate 2 by means of brazing. In this manner, an integrated cooling body 1 is constructed.
Now description is made hereinafter for operations of the apparatus described above. Temperature of the semiconductors 4a, 4b and 4c, which are parts of heat-radiating electronic equipment, are raised due to heat generated during operation of the apparatus. However, the heat is conducted through bases of the semiconductors to the cooling body 1, and is emitted from the entire surfaces of the fins 3. Because a number of fins 3 are used with a narrow inter-fin space (p) in the cooling body so that the surface area becomes larger, temperature of the semiconductors 4a, 4b and 4c for power can be maintained at an allowable level by forcefully sending cooling air to between the fins 3 by the cooling fan so that heat radiated from the surfaces of the fins 3 is conducted to the atmosphere.
Technological documents relating to this invention include the Japanese Patent Laid Open Publication No.18468/1991 disclosing a "Method of Connecting Heat Sinks", the Japanese Utility Model No.71984/1982 disclosing a "Stacked Heat Exchanger", the Japanese Patent Publication No.37877/1988 disclosing a "Radiator", the Japanese Utility Model Publication No.25893/1987 also disclosing a "Radiator", the Japanese Utility Model Laid Open Publication No.190047/1985 disclosing a "Radiator", and the Japanese Utility Model Laid Open Publication No.146451/1990 disclosing a "Radiator for Electronic Elements".
In the conventional type of cooling apparatus as described above, there are several problem arise. First, when arranging in parallel and brazing the ]-shaped fins to a flat plate, an appropriate tool must be used for positioning (temporally fixing) the ]-shaped fins to the flat plate. Second, when arranging in parallel the ]-shaped fins on a flat plate and temporally fixing them to the flat plate by means of brazing, as an edge face of one fin contacts a surface of a brazing material of another fin, if the brazing material is melted, a clearance is generated between fins. The clearance makes it difficult to accurately stack and fix the fins. The brazing process also may generate a displacement or fall of the fins, which in turn will make it impossible to braze the fins in their erect posture at correct positions. As a result, the working efficiency of the assembly becomes lower.